1. Field of the Invention
The present invention relates to an ink jet head. The present invention also relates to a piezo-electric actuator. Moreover, the present invention relates to a method of manufacturing the ink jet head and the piezo-electric actuator.
2. Description of the Related Art
Piezo-electric actuators are utilized for a variety of purposes. A piezo-electric actuator has electrodes formed at a top surface and a bottom surface of a layer (a piezo-electric layer) formed from a material that deforms when voltage is applied between the electrodes at the top surface and the bottom surface of the material. The shape of the piezo-electric layer can be changed by controlling the potential applied between the electrodes on the top surface and the bottom surface. Dividing at least one of the electrodes into a plurality of independent electrodes makes it possible to control the difference in potential applied to each part of the piezo-electric layer. One of the purposes of piezo-electric actuators is to drive an ink jet head used in an ink jet printer.
Ink jet printers are well known. An ink jet printer is provided with an ink jet head that discharges ink. A conventional ink jet head is taught in Japanese Patent Application Publication No. 11-334087 (1999-334087).
The ink jet head is provided with a channel body and the piezo-electric actuator. A plurality of ink flow channels is formed in the channel body. Each ink flow channel is provided with a pressure chamber and a nozzle connected with the pressure chamber. The pressure chambers are formed at a surface of the channel body and exposed to an outside of the channel body. The pressure chambers are distributed across the surface of the channel body.
The piezo-electric actuator is stacked on the channel body. The piezo-electric actuator has a broad, sheet shaped piezo-electric layer. The piezo-electric actuator seals the pressure chambers from atmosphere when stacked on the surface of the channel body. A plurality of first electrodes is disposed on a front surface of the piezo-electric layer in the same distribution pattern as that of the pressure chambers. A second electrode is disposed on a back surface of the piezo-electric layer. The second electrode covers approximately the entire back surface of the piezo-electric layer. In usual, the piezo-electric actuator is stacked on the channel body so that the second electrode is located between the piezo-electric layer and the channel body.
Applying voltage to one of these first electrodes deforms the piezo-electric layer at a location between the second electrode and the first electrode to which the voltage is being applied. When the first electrode to which the voltage is being applied is shifted, deforming portion within the piezo-electric layer is also shifted. That is, the piezo-electric actuator includes a plurality of piezo-electric elements, and each piezo-electric element deforms when voltage is applied to the first electrode of that piezo-electric element. A single piezo-electric element is formed from a combination of one of the first electrode, a part of the piezo-electric layer facing that first electrode, and a part of the second electrode facing that first electrode.
When the piezo-electric actuator is stacked on the channel body, each of the piezo-electric elements faces each of the pressure chambers. When the piezo-electric element expands, capacity of the pressure chamber corresponding to that piezo-electric element is reduced, pressure within that pressure chamber is increased, and ink is discharged from the nozzle connected to the pressurized pressure chamber.
Selection of the first electrode to which voltage is being applied causes a selection of the expanding location within the piezo-electric layer. In the ink jet head with the above configuration, it is possible to select a particular nozzle by selecting single first electrode to which voltage will be applied tom the plurality of first electrodes. It is also possible to control whether the selected nozzle discharges or does not discharge ink by changing the voltage applied to the selected first electrode.